Commuters catching the morning trains from Bridgeport, Conn. to Grand Central Station on Monday Feb. 11, 2013, had their choice of seats as the cars were nearly empty. Futher down the line toward Stamford, they started to fill up as service was limited and mostly local. less

Commuters catching the morning trains from Bridgeport, Conn. to Grand Central Station on Monday Feb. 11, 2013, had their choice of seats as the cars were nearly empty. Futher down the line toward Stamford, they ... more

Commuters catching the morning trains from Bridgeport, Conn. to Grand Central Station on Monday Feb. 11, 2013, had their choice of seats as the cars were nearly empty. Futher down the line toward Stamford, they started to fill up as service was limited and mostly local. less

Commuters catching the morning trains from Bridgeport, Conn. to Grand Central Station on Monday Feb. 11, 2013, had their choice of seats as the cars were nearly empty. Futher down the line toward Stamford, they ... more

Commuters catching the morning trains from Bridgeport, Conn. to Grand Central Station on Monday Feb. 11, 2013, had their choice of seats as the cars were nearly empty. Futher down the line toward Stamford, they started to fill up as service was limited and mostly local. less

Commuters catching the morning trains from Bridgeport, Conn. to Grand Central Station on Monday Feb. 11, 2013, had their choice of seats as the cars were nearly empty. Futher down the line toward Stamford, they ... more

Commuters catching the morning trains from Bridgeport, Conn. to Grand Central Station on Monday Feb. 11, 2013, had their choice of seats as the cars were nearly empty. Futher down the line toward Stamford, they started to fill up as service was limited and mostly local. less

Commuters catching the morning trains from Bridgeport, Conn. to Grand Central Station on Monday Feb. 11, 2013, had their choice of seats as the cars were nearly empty. Futher down the line toward Stamford, they ... more

During Tuesday morning's commute, Metro-North's New Haven line plans to increase service between South Norwalk and Grand Central Terminal to about 90 percent of normal conditions, with 75 percent of normal service on the Danbury line, and a full run on the New Canaan branch.

The scaled-back service is linked to deep snow at rail yards, preventing trains from emerging from the depots. Harsh weather conditions in the past led to breakdowns of the state's fleets of older M-2, M-4, and M-6 trains. On Monday, about 60 percent of the necessary fleets that operated were comprised of new M-8 cars.

"The gradual return of service is entirely due to the challenges of digging out of the yards and not to mechanical problems with older fleets," Metro-North spokeswoman Marjorie Anders said.

In the winters of 2010 and 2011, nearly 80 inches of snow in Connecticut paralyzed the New Haven Line, and at various points, more than half of the state's fleet of worn-out M-2, M-4, and M-6 cars were being repaired or out of service. The three older-model cars are vulnerable to breakdowns due to blowing snow, which can short out circuitry in vulnerable boxes beneath the trains or stall traction engines when it is sucked through cooling vents on the trains.

For the first morning rush hour since the Blizzard of 2013 hit, the New Haven Line resumed service between New Haven and Stamford Monday with half the normal inbound service.

Throughout the morning rush hour, the railroad reported scattered delays of up to 20 minutes, but said service was running on or close to schedule as of 10:40 a.m.

Anders said ridership on the outer New Haven Line was down about 50 percent Monday.

Around 8:20 a.m., a train originating in New Canaan and heading to Grand Central Terminal broke down near Woodlawn, N.Y., when a traction motor on the third of five M-6 cars on the run short-circuited, causing a "serious smoke condition" on board the car, forcing passengers to flee to cars in front and behind the damaged car, according to Anders.

Before all customers left the smoky car, several customers opened the four emergency windows on the car and the smoke on board dissipated quickly, Anders said. The train remained halted so crews could inspect it, but resumed its journey and arrived about 39 minutes late, Anders said.

The cause of the breakdown is still being determined, but the type of malfunction is common during snowy conditions and often caused by water in the motor, Anders said.

Marty St. George, a New Canaan commuter, said passengers in the car described seeing flames and electricity arcing from the failed motor after leaving the car. Anders said the short circuit automatically shut down the fuse, snuffing the flames.

"There was no need for a Fire Department response and no fire extinguisher was used or needed," Anders said. "A traction motor is the component which transforms electricity into movement. When it grounds out, essentially blows a fuse, it turns itself off. Once the power is off, it does not continue."

After being shut down at 10 p.m. Friday, service between New Haven and Stamford remained suspended until Monday morning due to the deep snowfall that buried rail yards in New Haven and Bridgeport.

On Monday, Metro-North continued work geared to ensuring the system's trains and rights of way operated smoothly after the storm-enforced shutdown.

Crews continued to further clear deep snow from rail yards in New Haven and Bridgeport and to clear track switches that allow trains to emerge from the depots, according to Metro-North.

Two jet engine snow blowers, two front end loaders, and several triple axle trucks continued to clean off rail cars in the yards, including clearing the pantograph mechanical arms atop the trains which are used to draw power from overhead lines, according to the railroad.